全文获取类型
收费全文 | 40690篇 |
免费 | 15771篇 |
国内免费 | 79篇 |
专业分类
化学 | 53449篇 |
晶体学 | 37篇 |
力学 | 1093篇 |
数学 | 1208篇 |
物理学 | 753篇 |
出版年
2024年 | 422篇 |
2023年 | 4246篇 |
2022年 | 1403篇 |
2021年 | 2406篇 |
2020年 | 4671篇 |
2019年 | 2219篇 |
2018年 | 2370篇 |
2017年 | 602篇 |
2016年 | 5542篇 |
2015年 | 5503篇 |
2014年 | 4921篇 |
2013年 | 5088篇 |
2012年 | 3060篇 |
2011年 | 1004篇 |
2010年 | 3321篇 |
2009年 | 3264篇 |
2008年 | 1044篇 |
2007年 | 741篇 |
2006年 | 202篇 |
2005年 | 147篇 |
2004年 | 104篇 |
2003年 | 104篇 |
2002年 | 71篇 |
1997年 | 62篇 |
1996年 | 69篇 |
1995年 | 137篇 |
1994年 | 80篇 |
1993年 | 196篇 |
1992年 | 98篇 |
1991年 | 70篇 |
1988年 | 97篇 |
1987年 | 79篇 |
1985年 | 66篇 |
1984年 | 86篇 |
1983年 | 74篇 |
1982年 | 91篇 |
1981年 | 98篇 |
1980年 | 111篇 |
1979年 | 116篇 |
1978年 | 118篇 |
1977年 | 184篇 |
1976年 | 190篇 |
1975年 | 191篇 |
1974年 | 203篇 |
1973年 | 118篇 |
1972年 | 157篇 |
1971年 | 125篇 |
1970年 | 213篇 |
1969年 | 129篇 |
1968年 | 138篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
931.
Dr. Yoshinobu Kamakura Dr. Chomponoot Suppaso Issei Yamamoto Ryusuke Mizuochi Yusuke Asai Prof. Dr. Teruki Motohashi Prof. Dr. Daisuke Tanaka Prof. Dr. Kazuhiko Maeda 《Angewandte Chemie (International ed. in English)》2023,62(28):e202305923
Certain metal complexes are known as high-performance CO2 reduction photocatalysts driven by visible light. However, most of them rely on rare, precious metals as principal components, and integrating the functions of light absorption and catalysis into a single molecular unit based on abundant metals remains a challenge. Metal-organic frameworks (MOFs), which can be regarded as intermediate compounds between molecules and inorganic solids, are potential platforms for the construction of a simple photocatalytic system composed only of Earth-abundant nontoxic elements. In this work, we report that a tin-based MOF enables the conversion of CO2 into formic acid with a record high apparent quantum yield (9.8 % at 400 nm) and >99 % selectivity without the need for any additional photosensitizer or catalyst. This work highlights a new MOF with strong potential for photocatalytic CO2 reduction driven by solar energy. 相似文献
932.
Wei Zheng Prof. XuPing Li Dr. Glib V. Baryshnikov Xueru Shan Dr. Farhan Siddique Dr. Cheng Qian Prof. Shengyin Zhao Prof. Hongwei Wu 《Angewandte Chemie (International ed. in English)》2023,62(32):e202305925
It is challenging to achieve stable and efficient radical emissions under ambient conditions. Herein, we present a rational design strategy to protect photoinduced carbonyl free radical emission through electrostatic interaction and spin delocalization effects. The host-guest system is constructed from tricarbonyl-substituted benzene molecules and a series of imidazolium ionic liquids as the guest and host, respectively, whereby the carbonyl anion radical emission can be in situ generated under the light irradiation and further stabilized by electrostatic interaction. More importantly, the anion species and the alkyl chain length of imidazolium ionic liquids show a noticeable effect on luminescence efficiency, with the highest radical emission efficiency is as high as 53.3 % after optimizing the imidazole ionic liquid's structure, which is about four times higher than the polymer-protected radical system. Theoretical calculations confirm the synergistic effect of strong electrostatic interactions and that the spin delocalization effect significantly stabilizes the radical emission. Moreover, such a radical emission system also could be integrated with a fluorescent dye to induce multi-color or even white light emission with reversible temperature-responsive characteristics. The radical emission system can also be used to detect different amine compounds on the basis of the emission changes and photoactivation time. 相似文献
933.
Dr. Greggory T. Kent Emily Morgan Kaitlin R. Albanese Dr. Anna Kallistova Dr. Alexandra Brumberg Linus Kautzsch Dr. Guang Wu Prof. Pratap Vishnoi Prof. Ram Seshadri Prof. Anthony K. Cheetham 《Angewandte Chemie (International ed. in English)》2023,62(32):e202306000
Halide double perovskites [A2MIMIIIX6] are an important class of materials that have garnered substantial interest as non-toxic alternatives to conventional lead iodide perovskites for optoelectronic applications. While numerous studies have examined chloride and bromide double perovskites, reports of iodide double perovskites are rare, and their definitive structural characterization has not been reported. Predictive models have aided us here in the synthesis and characterization of five iodide double perovskites of general formula Cs2NaLnI6 (Ln=Ce, Nd, Gd, Tb, Dy). The complete crystal structures, structural phase transitions, optical, photoluminescent, and magnetic properties of these compounds are reported. 相似文献
934.
Guodong Chen Jinran Sun Jiedong Li Dr. Xiaofan Du Gaojie Xu Prof. Shanmu Dong Prof. Guanglei Cui 《Angewandte Chemie (International ed. in English)》2023,62(31):e202306141
The Germanium (Ge), as a fast-charging and high specific capacity (1568 mAh g−1) alloy anode, is greatly hampered in practical application by poor cyclability. To date, the understanding of cycling performance degradation remains elusive. This study illustrates that, contrary to conventional beliefs, most of the Ge material in failed anodes still retains good integrity and does not undergo severe pulverization. It is revealed that capacity degradation is clearly correlated to the interfacial evolution of lithium hydride (LiH). Tetralithium germanium hydride (Li4Ge2H), as a new species derived from LiH, is identified as the culprit of Ge anode degradation, which is the dominant crystalized component in an ever-growing and ever-insulating interphase. The significantly increased thickness of the solid electrolyte interface (SEI) is accompanied by the accumulation of insulating Li4Ge2H upon cycling, which severely retards the charge transport process and ultimately triggers the anode failure. We believe that the comprehensive understanding of the failure mechanism presented in this study is of great significance to promoting the design and development of alloy anode for the next generation of lithium-ion batteries. 相似文献
935.
Christina Wartmann Dr. Shiny Nandi Dr. Jörg-Martin Neudörfl Prof. Dr. Albrecht Berkessel 《Angewandte Chemie (International ed. in English)》2023,62(35):e202306584
The titanium complex of the cis-1,2-diaminocyclohexane (cis-DACH) derived Berkessel-salalen ligand is a highly efficient and enantioselective catalyst for the asymmetric epoxidation of terminal olefins with hydrogen peroxide (“Berkessel-Katsuki catalyst”). We herein report that this epoxidation catalyst also effects the highly enantioselective hydroxylation of benzylic C−H bonds with hydrogen peroxide. Mechanism-based ligand optimization identified a novel nitro-salalen Ti-catalyst of the highest efficiency ever reported for asymmetric catalytic benzylic hydroxylation, with enantioselectivities of up to 98 % ee, while overoxidation to ketone is marginal. The novel nitro-salalen Ti-catalyst also shows enhanced epoxidation efficiency, as evidenced by e.g. the conversion of 1-decene to its epoxide in 90 % yield with 94 % ee, at a catalyst loading of 0.1 mol-% only. 相似文献
936.
Shuang Guo Dr. Yeonju Park Eungyeong Park Dr. Sila Jin Prof. Lei Chen Prof. Young Mee Jung 《Angewandte Chemie (International ed. in English)》2023,62(34):e202306709
π-Conjugated organic semiconductors are promising materials for surface-enhanced Raman scattering (SERS)-active substrates based on the tunability of electronic structures and molecular orbitals. Herein, we investigate the effect of the temperature-mediated resonance-structure transitions of poly(3,4-ethylenedioxythiophene) (PEDOT) in poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT : PSS) films on the interactions between substrate and probe molecules, thereby affecting the SERS activity. Absorption spectroscopy and density functional theory calculations show that this effect occurs mainly due to delocalization of the electron distribution in molecular orbitals, effectively promoting the charge transfer between the semiconductor and probe molecules. In this work, we investigate for the first time the effect of electron delocalization in molecular orbitals on SERS activity, which will provide new design ideas for the development of highly sensitive SERS substrates. 相似文献
937.
Jiahui Xian Suisheng Li Hui Su Peisen Liao Shihan Wang Runan Xiang Yawei Zhang Prof. Qinghua Liu Prof. Guangqin Li 《Angewandte Chemie (International ed. in English)》2023,62(30):e202306726
The conversion of industrial exhaust gases of nitrogen oxides into high-value products is significantly meaningful for global environment and human health. And green synthesis of amino acids is vital for biomedical research and sustainable development of mankind. Herein, we demonstrate an innovative approach for converting nitric oxide (NO) to a series of α-amino acids (over 13 kinds) through electrosynthesis with α-keto acids over self-standing carbon fiber membrane with CoFe alloy. The essential leucine exhibits a high yield of 115.4 μmol h−1 corresponding a Faradaic efficiency of 32.4 %, and gram yield of products can be obtained within 24 hours in lab as well as an ultra-long stability (>240 h) of the membrane catalyst, which could convert NO into NH2OH rapidly attacking α-keto acid and subsequent hydrogenation to form amino acid. In addition, this method is also suitable for other nitrogen sources including gaseous NO2 or liquidus NO3− and NO2−. Therefore, this work not only presents promising prospects for converting nitrogen oxides from exhaust gas and nitrate-laden waste water into high-value products, but also has significant implications for synthetizing amino acids in biomedical and catalytic science. 相似文献
938.
Guangming Wang Shunhua Chen Qiwei Duan Fenfei Wei Prof. Sen Lin Prof. Zailai Xie 《Angewandte Chemie (International ed. in English)》2023,62(38):e202307470
Borocarbonitride (BCN) materials are newly developed oxidative dehydrogenation catalysts that can efficiently convert alkanes to alkenes. However, BCN materials tend to form bulky B2O3 due to over-oxidation at the high reaction temperature, resulting in significant deactivation. Here, we report a series of super stable BCN nanosheets for the oxidative dehydrogenation of propane (ODHP) reaction. The catalytic performance of the BCN nanosheets can be easily regulated by changing the guanine dosage. The control experiment and structural characterization indicate that the introduction of a suitable amount of carbon could prevent the formation of excessive B2O3 from BCN materials and maintain the 2D skeleton at a high temperature of 520 °C. The best-performing catalyst BCN exhibits 81.9 % selectivity towards olefins with a stable propane conversion of 35.8 %, and the propene productivity reaches 16.2 mmol h−1 g−1, which is much better than hexagonal BN (h-BN) catalysts. Density functional theory calculation results show that the presence of dispersed rather than aggregated carbon atoms can significantly affect the electronic microenvironment of h-BN, thereby boosting the catalytic activity of BCN. 相似文献
939.
Dr. Meng Lu Shuai-Bing Zhang Ming-Yi Yang Yu-Fei Liu Jia-Peng Liao Pei Huang Dr. Mi Zhang Prof. Shun-Li Li Prof. Zhong-Min Su Prof. Ya-Qian Lan 《Angewandte Chemie (International ed. in English)》2023,62(31):e202307632
In this work, we innovatively assembled two types of traditional photosensitizers, that is pyridine ruthenium/ferrum (Ru(bpy)32+/Fe(bpy)32+) and porphyrin/metalloporphyrin complex (2HPor/ZnPor) by covalent linkage to get a series of dual photosensitizer-based three-dimensional metal-covalent organic frameworks (3D MCOFs), which behaved strong visible light-absorbing ability, efficient electron transfer and suitable band gap for highly efficient photocatalytic hydrogen (H2) evolution. Rubpy-ZnPor COF achieved the highest H2 yield (30 338 μmol g−1 h−1) with apparent quantum efficiency (AQE) of 9.68 %@420 nm, which showed one of the best performances among all reported COF based photocatalysts. Furthermore, the in situ produced H2 was successfully tandem used in the alkyne hydrogenation with ≈99.9 % conversion efficiency. Theoretical calculations reveal that both the two photosensitizer units in MCOFs can be photoexcited and thus contribute optimal photocatalytic activity. This work develops a general strategy and shows the great potential of using multiple photosensitive materials in the field of photocatalysis. 相似文献
940.
Xiang-Zhu Wei Tian-Yu Ding Dr. Yang Wang Dr. Bing Yang Dr. Qing-Qing Yang Prof. Dr. Shengfa Ye Prof. Dr. Chen-Ho Tung Prof. Dr. Li-Zhu Wu 《Angewandte Chemie (International ed. in English)》2023,62(36):e202308192
High-valent iron-oxo species are appealing for conducting O−O bond formation for water oxidation reactions. However, their high reactivity poses a great challenge to the dissection of their chemical transformations. Herein, we introduce an electron-rich and oxidation-resistant ligand, 2-[(2,2′-bipyridin)-6-yl]propan-2-ol to stabilize such fleeting intermediates. Advanced spectroscopies and electrochemical studies demonstrate a high-valent FeV(O) species formation in water. Combining kinetic and oxygen isotope labelling experiments and organic reactions indicates that the FeV(O) species is responsible for O−O bond formation via water nucleophilic attack under the real catalytic water oxidation conditions. 相似文献